Autohelm ST4000

[CG]

Has been working fine until now, control head will not power up.
As soon I trip beaker for Auto Pilot fuse blows.

Any ideas what may be wrong.

Thanks
CG

[Ken Juul]

It is probably something wrong with the control head.  With age they tend to leak and then short out.  But it might be the supply wire.  Before you do any surgery on the head, disconnect the power wires and see it the CB still pops.  If yes, bad wire, no.... bad control head.  I don't think Raymarine repairs the ST4000 any more.   But it wouldn't hurt to give them a call.  The other option is to open it up and see if it is something obvious that can be repaired.  Maybe a local marine electronics repair guy still has the schematics.

[CG]

Thanks for the reply,  I have disconnected control head from power source, and CB did not pop.
I was able to power up Control head from a alternate power soruce.
I will give Raymarine call.
Thanks

[Ken Juul]

Glad it powered up.  Did the separate source have a CB in the circuit?  If yes, same or different size?  Perhaps it was just corrosion causing high resistance causing the CB to pop.  May want to clean up the connections and try again.  If it still pops, then look down line from the control head.  If I remember correctly, the ST4000 cycles the motor right after start up to move the wear spot on the belt.  Maybe the motor is or it's power line are the problem.

[Indian Falls]

Double check the integrity of the plugs to see if you have a pin pushed out or in.  Could be when you plug in your control, the pins in the receptacle make contact with each other setting off the breaker.  High resistance will make heat and drop voltage, current will remain the same.

I have a schematic for this in my collection of autohelm paperwork,  it's not likely to do any good though.  I dont think the problem is in the control if it runs off another dc source.  How did you connect it?  Have you done a continuity test on the boat where the CB is? Lift one lead and ohm out the path to the control when its all hooked up. Let us know if you have 50 ohms or 2 ohms.  What is the CB or fuse size?  5 amp?  1 amp? 

Good luck!

[CG]

Ken
Control head did power up, but no CB. I had it wired directly to a 12volt battery.

It seem to operate fine.